1. Field of the Invention
In a first aspect, this invention relates to a tool intended for chip removing or cutting machining and of the type that includes two parts oriented along a common center axis and detachably connected to each other via a threaded joint. The threaded joint includes, on one hand, a female thread positioned in the vicinity of a mouth in a hollow space in one of the parts, and on the other hand a male thread positioned in the vicinity of a free end of a male-like pin included in the other part. The individual thread includes a helicoidal ridge, which has a top and a pair of opposite flanks, which delimit a likewise helicoidal groove having a bottom. A first flank of the male thread ridge, which faces away from the end of the pin, is pressed against a first flank of the female thread ridge, which faces away from the mouth of the hollow space, in connection with screwing-in of the pin into the hollow space. And the second flank of the male thread ridge, which faces the free end of the pin, is pressed against a second flank of the female thread ridge, which faces the mouth, in connection with unscrewing of the pin.
In another aspect, the invention also relates to a detachable part for such tools.
In practice, tools of this type may be used for machining work pieces of metal, such as steel and steel alloys, iron, aluminium, titanium, etc.
2. Description of Related Art
Related rotatable cutting tools include two parts connected via an interface or joint. For example, a basic body and a cutting body or wear part are detachably connected together. In practice, such tools may be in the form of drills or milling cutters, e.g., shank-end or profile mills. In moderm machine tools, the basic bodies are so expensive that they, for economical reasons, cannot be integrated with the cutting body, which is a wear part and therefore has a limited service life. In other words, it is profitable to make the proper cutting body in the form of a separate unit, which those skilled in the art usually refer to as a “loose top,” and which can be exchanged after wear, while the basic body can be utilized for a longer time.
The development of loose-top tools for rotary machining has lately been intense and resulted in a number of different tool constructions, which differ from each other primarily in respect to the interface or the joint between the loose top and the basic body. It is believed that insofar as loose-top tools have been the object of a large number of proposals for design solutions, is per se evidence of the design of the interface between the loose top and the basic body is a technical problem that is difficult to master. Thus, consideration has to be given to a number of different difficulties, which are based not only on the circumstance that the loose top and the basic body are manufactured from different materials and in production units separated from each other, but also on the circumstance that the tools should operate under severe external conditions, such as strong heat release, the influence from large cutting forces, and the like. In particular, such small tools as shank-end and profile mills are subjected to a variety of different stresses, which vary most considerably in different functional states. Thus, the loose top, i.e., the hard, detachable cutting body of, for instance, a profile mill, is subjected not only to axial tensile and compressive forces, respectively, but also to miscellaneous radial forces acting at different angles to the loose top. Therefore, to form a practically working interface or joint between a loose top and a basic body becomes a delicate balance between a number of, at times conflicting, desires.
In related tools, threaded joints have been used with varying success in order to connect the loose top with the basic body. Usually, a rear, male-like pin is formed on the loose top having a conical or cylindrical male thread, which can be screwed into a corresponding female thread in a hollow space, which mouths in a front end of the basic body. In related tools, the rear pin of the loose top is formed with external, cylindrical guide surfaces in front of and behind the male thread of the pin. When the male thread is tightened in the female thread of the basic body, the guide surfaces are brought into engagement with internal, cylindrical guide surfaces in front of and behind, respectively, the female thread with the purpose of stably anchoring the loose top, and above all, counteracting deflection of the same, when it is subjected to radial stresses. In one related tool, a threaded joint has conical threads. Characteristic of this threaded joint is that the top of one of the threads should have surface contact with the groove bottom of the other thread with the purpose of anchoring the loose top and counteracting deflection of the same. In theory, this is an attractive idea, so far that the number of co-operating guide surfaces can be reduced. However, in practice, the manufacture of the two tool parts requires too a high dimensional accuracy in order for a serial production to be at least economically realistic. In a related cutting tool, the loose top includes a single conical guide surface adjacent to the male thread of the pin.
Common to all previously known threaded joints for cutting tools, is that the force by which the threads force the loose top to move axially is equally large upon screwing-in (when the threads act pullingly) as upon unscrewing (when the threads act pressingly), and that the threads may be deformed if they are overloaded by too powerful tightening.